Excess heat is one of the primary causes of failure for microprocessors. Generally, the life of a microprocessor is a function of the thermal load applied during its use. Excessive heat results in internal breakdown of the processor circuits, eventually resulting in failure. With the introduction of processors with sub-micron circuit elements, ever-increasing transistor count (e.g., 42 million transistors for an Intel Pentium 4™ processor) and operating speed, the problem of preventing processor failure due to excess heat is exacerbated.
The objective of thermal management is to ensure that the temperature of all components in a system are maintained with their functional temperature range. Within this temperature range, a component, and in particular its electrical circuits, is expected to meet its specified performance. Operation outside of the functional temperature range can degrade system performance, cause logic errors, or cause component and/or system damage. Temperature exceeding the maximum operating limit of a component may result in irreversible changes in the operating characteristics of the component.
A common way to verify a thermal solution for a particular platform/processor begins with thermal design parameters for the processor type. Generally, a processor produces a baseline amount of heat by simply being powered (i.e., when in a sleeping state), and a variable amount of heat that is a function of the processing load encountered during operation. Other factors include the operating frequency, and structural parameters, such as circuit line width and density. Notably, different processors of the same design may exhibit significantly different thermal characteristics. In order to ensure processor longevity, the processor manufacture publishes various thermal design parameters that are derived from an extensive statistical-based testing of each processor type. For example, thermal design parameters such an overall minimum heat transfer coefficient, maximum temperature, and thermal design power ratings are specified by the manufacturer for a particular processor model.
Based (generally, at least in part) on these thermal design parameters, Engineers for system integrators (e.g., a original equipment manufacturer such as Hewlett-Packard, Dell, Compaq, IBM, Toshiba, Gateway, etc.) use these thermal design parameters to verify that their platform's thermal solution will provide sufficient cooling to ensure processor longevity. While this is generally not as much of an issue for desktop computer systems, which typically provide thermal solutions having large cooling margins, such large cooling margins are not realizable for laptop and notebook computers. Accordingly, it is generally necessary to verify the thermal design via testing, preferably using a statistically significant number of test samples to account for the variance in processor power. Under conventional testing techniques, this typically requires the use of various external instrumentation and thermal test components, including resistive thermal devices (RTDs) such as thermocouples or thermisters to measure the external processor temperature, electronic test equipment to measure and record the test results, etc. This type of thermal solution verification testing is both expensive and time-consuming.